Nikon Creative Lighting System (CLS) How does it work?

[walterpike]

Everything you read about the CLS is about how amazing it is. I have been discussing this on another thread but want to hone into some specifics - and specifically the TTL settings.

In principle as I understand it; the camera reads the light in the scene. Then communicates with all the off camera flashes with how much light they need to add to the scene to get the exposure you want - you set the ratios with the compensation settings.

How does it do this? For example where is it getting the data. From the remote flashes? So what happens when the sensor window is pointing toward an umbrella (and has to because the trigger sensor has to face the commander unit) or when the flash is being bounced off a reflector or through a diffuser.

If the camera is telling the flash when to switch off how does it do that in the very small time it has.

I have read a lot - but most tell you how to set up - not this.

Thank you.

[Leo Theron]

Walter,

I half-answered this in the 'other thread'

But the CLS trick lies in the the pre-exposure flash. The commander fires a measuring flash, each group: A, B, C in succession. Using that information, the camera - not the flash- then calculates the ambient light exposure required as well as that required from each flash, with the compensation as you have set it, using iTTL. The commander then issues the flash command for groups A,B and C and they all fire together at the calculated power. And if your compensation was crooked - your images will b*ggered.

This all is encoded in an IR stream of commands - and it works because the measurement it is a closed loop system. You must just assure that the flash can pick up the IR command stream, and it can be reflected! Best is if the small window on the side of the flash can see the IR stream from the commander. AS you know by now - a CLS commander can be the SU-800 or commander flash (pop-up or SB-6/7/900 and 910.

When you issue manual flash commands for each group (M) by setting the power levels, it does just that - Simply fires the flash as you set it.

I got a special model (Pop) in to understand CLS. It helped a lot. Results are here: http://www.pbase.com/leot/pop

[Warren Williams]

If you go here you will find all the answers

http://nikonclspracticalguide.blogspot.com/

[walterpike]

Walter,

I half-answered this in the 'other thread'

I got a special model (Pop) in to understand CLS. It helped a lot. Results are here: http://www.pbase.com/leot/pop

Thank you - that makes sense. I now understand.

[walterpike]

If you go here you will find all the answers

http://nikonclspracticalguide.blogspot.com/

Thank you - I looked there and found some answers. I bought a book on the CLS - I didn't pick up this point. Blog 6 kind of explained. Will read the rest as well.

[walterpike]

Thank you - that makes sense. I now understand.

Leo - there was such a small gap in my knowledge, I have been playing around taking pictures of my mannequin head and quess what, it's working just fine, doing exactly what it supposed to do and I feel as confident as when I am using my studio monolights. Certainly for the portrait like pics I have been trying with. Thanks for the patience.